New Organisms/Life Forms

New Organisms With Synthetic DNA Could Lead to Entirely New Life Forms

Two synthetic base pairs have been added to the DNA of E. coli, and the microbes are thriving.

By Jay Bennett

Scientists continue to inch closer and closer to medical breakthroughs by tinkering with DNA. At the end of 2016, the CRISPR gene-editing tool was used for the first time on human cancer patients, and now, researchers have succeeded in creating a new kind of life with partially synthetic DNA.

The E. coli microbes with synthetic DNA have an additional, lab-created "base pair" of molecules that researchers hope can be programmed so the organism produces new types of proteins that can be made into drugs. The research was published Monday in the journal Proceedings of the National Academy of Sciences.

A DNA strand is a large molecule of nucleic acid that contains the genetic instructions used by all living organisms to grow, develop, and reproduce. Despite the wide diversity of life on Earth, there are only four letters in the genetic alphabet: A, T, C and G. These four molecular bases—adenine, thymine, cytosine and guanine—pair with each other using hydrogen bonds to form the foundation for a DNA strand.

There are only the two base pairs—A bonds with T, and C bonds with G—that provide the structure of a DNA double helix. Organic molecules called nucleotides bond to the base pairs to create the complete genetic code for life. The base pairs can be thought of as the rungs in the DNA ladder, and variations in life have everything to do with what order they are arranged in.

For the first time, scientists have created a stable organism with a new base pair that uses synthetic bases, labeled X and Y. The E. coli microbes created by the Scripps Research Institute in California use the conventional genetic alphabet, A, T, C and G, as well as the new X and Y "nucleobases" that do not occur in nature.

THE NEW MICROBES ARE THE FIRST STEP TO "CREATE ORGANISMS WITH WHOLLY UNNATURAL ATTRIBUTES AND TRAITS NOT FOUND ELSEWHERE IN NATURE"

The report published Monday says the new microbes are the first step to "create organisms with wholly unnatural attributes and traits not found elsewhere in nature" and "lay the foundation for achieving the central goal of synthetic biology: the creation of new life forms and functions," as reported by The Guardian.

The Scripps Research Institute actually created the first organism with synthetic DNA bases almost three years ago, but those organisms would die off quickly and could not regularly pass the new genetic bases on when reproducing. The new E. coli microbes are the first semi-synthetic organisms that can divide and thrive like normal while passing on the synthetic material.

The microbes were first genetically modified to absorb the new genetic material, and then the X and Y molecules, created separately from the microbes, were fed to the E. coli. This method of introducing the new genetic material also works as a failsafe, as the microbes cannot produce the X and Y molecules on their own and must be sustained in a lab to survive.

At this point, the synthetic bases don't do anything except survive in the microbes and get passed on when the bacteria divides. Among other tweaks to the process since 2014, the researchers got the bacteria to successfully pass on the synthetic DNA bases by modifying the microbe's immune system with CRISPR so any DNA strands without the X and Y bases would be destroyed.

THE NEXT STEP IS TO TRICK THE ORGANISMS INTO READING THE SYNTHETIC DNA CODE

The next step is to trick the organisms into reading the synthetic DNA code, causing them to create new proteins that do not occur in nature. To do this, scientists are going to need to transcribe the new synthetic DNA bases into RNA counterparts, as RNA molecules are what allow organisms to read DNA and produce proteins. This type of laboratory protein farming could lead to the development of new drugs to treat a wide variety of ailments.

"This is a major step forward in showing that a living cell such as a simple bacterium can be engineered to sustain a synthetic base pair not found in nature," Paul Freemont, a synthetic biology professor at Imperial College in London, told The Guardian. "This leads to the concept of semi-synthetic living systems that could be engineered to perform specific functions that would rely on a distinct genetic code compared to the natural genetic code."

Ultimately, the future could be much more bizarre. According to the new study, it is theoretically possible to create organisms with multiple synthetic base pairs like X and Y, further changing the organism's properties. It could even be possible to build an organism from scratch using nothing but human-designed genetic material.

Currently, the work only allows this kind of synthetic material to be inserted into single-celled organisms. That said, scientists continue to get better at breaking down the genetic codes of life and rebuilding them—or building synthetic versions—a trend that is likely to gain speed in the coming decades.

"We can now get the light of life to stay on," said Floyd Romesberg, lead scientist for the new organisms, in a Scripps Research Institute report. "That suggests that all of life's processes can be subject to manipulation."

Source: Scripps Research Institute via The Guardian